In recent years, the use of a cellular phone having a camera has expanded. A portable device is provided with a lens drive device for driving and moving a lens in an optical axis direction. The lens drive device includes a movable lens body provided with a lens, a fixed body which movably supports the movable lens body in an optical axis direction through a plate spring, and a magnetic drive mechanism for driving the movable lens body in the optical axis direction. The plate spring includes an outer side connection part which is connected with the fixed body, an inner side connection part which is formed in a circular ring frame shape and connected with the movable lens body, and a plurality of arm parts which connects the outer side connection part with the inner side connection part. In the arm part, straight line portions which are extended in a circumferential direction or in a tangential direction are formed so as to have a plurality of zigzag turns on an outer peripheral side of the movable lens body (see Japanese Patent Laid-Open No. 2006-201525 and Japanese Patent Laid-Open No. 2006-227103).
In the plate spring as structured as described above, the arm part is extended between the outer side connection part and the inner side connection parts to exert elasticity. In this manner, the plate spring controls a moving amount in the optical axis direction of the movable lens body when the movable lens body is moved in the optical axis direction. Further, a portable device is easily subjected to vibration or impact because of property of being portably carried, but the vibration or the impact is absorbed by the arm part.
The present inventors propose a plate spring having a shape which is capable of coping with a case where an outside shape of a lens drive device is a rectangular parallelepiped shape. In this case, the plate spring is disposed in a small area which is sandwiched between a fixed body whose cross section in a direction perpendicular to the optical axis is in a rectangular shape and a movable lens body whose outer peripheral shape is circular. Therefore, in the plate spring, a space between the outer side connection part which is connected with the fixed body and the inner side connection part which is connected with the movable lens body becomes small and thus degree of freedom of design for the shape of the arm part and the like is decreased. Accordingly, like the structure as described in the above-mentioned Patent References, in the plate spring in which straight line portions of the arm part extended in the circumferential direction or in the tangential direction are formed so as to have a plurality of zigzag turns on an outer peripheral side of the movable lens body, the number of turning portions is reduced and thus sufficient elasticity cannot be secured. In addition, when the lens drive device receives a strong impact such as a dropping impact to cause the movable lens body to be moved intensely in a direction perpendicular to the optical axis direction or in a tilt direction, plastic deformation or breaking may easily occur in the plate spring and malfunction such as stroke failure may easily occur in the lens drive device.